MiG-21 radar nerfed?

Regarding MiG-21 it has a prevention of tracking objects which are approaching in a +-150km/h window relative to the speed at which the ground approaches. It will detect targets at any speed in the scanning mode.

 

Interesting. Is this how it's behaving in DCSW as well? Because the manual seems to dedicate only this small chapter to the LST button:

 

"If you are engaging slow flying targets such as slow flying aircraft, helicopters or some unmanned

aerial vehicles (UAVs), or you are pursuing the aircraft with small relative speed, press the LST

button (CM50) while in search mode. LST stands for Low Speed Target which is a literal translation

of the Russian МСЦ label."

The DCS modeling is wrong as a slow target is not displayed with LST off. I made a bug tracker ticket but it was marked completed without a change. Of course when attacking a slow target you'd want to enable LST since you'd want to track it with the radar at some point.

Finally, the changelog has been updated: https://forums.eagle.ru/showthread.php?t=185366&page=2

 

Thanks !

 

The september update mainly relates to the radar. We can recoup now.

Finally, the changelog has been updated: https://forums.eagle.ru/showthread.php?t=185366&page=2

 

Thanks !

 

The september update mainly relates to the radar. We can recoup now.

 

Very good news, long waited update!

Very good news, long waited update!

The update came in September. It's just the patch notes that arrived now.

The update came in September. It's just the patch notes that arrived now.

 

Yeah I figured out this too late lol.

Correct, the 150 km/h limitation is a tracking issue not a detection issue. If you fly behind a 75km/h contact it will produce a blip on scanning radar to see. However if you try to try to lock on the radar will reject it as chaff or other undesirable false contact.

 

The LST button turns off this chaff-tracking protection so it is possible to lock on to slow contacts (chaff, clutter, or legitimately slow aircraft). But in all cases the slow contact is displayed the same as a fast one in the scanning mode.

 

F-5 detection with MiG-21bis module has been problematic. In some versions of the software an F-5 next to another aircraft (e.g. F-15) the F-15 is displayed but the F-5 is not. So every test for general radar performance should be done against a type other than F-5. F-5 may be a special case of behavior.

 

A test at 4km trail of a MiG-21bis and F-5 in 1000m spread formation. At a 160m stepdown the player MiG-21 displays the MiG-21 at ranges only less than 25,000m. The F-5 however appears at ranges disappears from the scope as range increases beyond ~28.5km.

 

By using the AI follow command to enforce a formation of different types in exact relative position it is shown that the MiG-21bis radar has different behavior for different target types.

 

 

 

I see . All of the Problems I have described were against F5s. The Mig 21 and F5 we have in DCS are near perfect opponents.

Edited November 26, 2017 by Dirty Rotten Flieger

Also thanks for the education Beam scanner. I have never understood why the Mig21 radar will not show targets that are above the horizon when the Mig is flying very low. You description of the side lobes interference is the first plausible explanation I have come across.

 

I have tested the F5 radar and it will detect contact if they are above the horizon no matter how low the F5 is flying. Maybe the mig21 radar is actually modeled in higher detail.

Also thanks for the education Beam scanner. I have never understood why the Mig21 radar will not show targets that are above the horizon when the Mig is flying very low. You description of the side lobes interference is the first plausible explanation I have come across.

 

I have tested the F5 radar and it will detect contact if they are above the horizon no matter how low the F5 is flying. Maybe the mig21 radar is actually modeled in higher detail.

The F5 had a superior radar - in particular a monopulse slotted array antenna. How much difference this makes and in which way in terms of search I'm not entirely certain; for the case you are describing, this antenna presents much smaller sidelobes and much faster target position processing compared to a con scan radar with parabolic antenna (correct me if I got that wrong for the 21s radar).

 

Smaller sidelobes means less self interference from ground bounce when flying low - however the effects of this are real and are shown in the 159s real life test results. Detection ranges get shorter the lower you're flying.

Edited November 26, 2017 by GGTharos

The F5 had a superior read - in particular a monopulse slotted array antenna. How much difference this makes and in which way in terms of search I'm not entirely certain; for the case you are describing, this antenna presents much smaller sidelobes and much faster target position processing compared to a con scan radar with parabolic antenna (correct me if I got that wrong for the 21s radar).

 

Smaller sidelobes means less self interference from ground bounce when flying low - however the effects of this are real and are shown in the 159s real life test results. Detection ranges get shorter the lower you're flying.

 

The MiG-21bis uses the RP-22, which is a monopulse radar with cassegrain antenna.

That would definitely make a difference IMHO. Even going from parabolic to slotted array on the F5 was a significant change and I believe we have the numbers for that.

The altitude clutter line that I mentioned has nothing to do with the Jaybird radar (RP-22?).. I only brought that up because people here brought up radars struggling to detect matching speed targets.

 

The altitude clutter line only affects pulse doppler radars, because only pulse doppler radars measure the doppler spectrum. The Jaybird is not a pulse doppler radar, and thus would not suffer from this problem.

 

That being said, old school pulse radars, like the Jaybird, have to deal with a lot of clutter that could saturate the reciever. One technique used to compensate for this was AGC, or Auto-Gain Control. Sidelobes exist on all antennas and can allow ground reflections to seep into the receiver. Being closer to the ground would mean more noise from the sidelobes which could trigger the AGC to lower the receivers gain. Doing so could prevent a weak target from making past the detector.

 

Now, obviously DCS is not simulating these physics and we have no means to determine how degraded the Jaybird would be at low altitude.

 

That being said, the radar uses a small parabolic cassegrain antenna, so it's safe to assume it's going to have decent size sidelobes (compared to slotted array designs being used by the west at the time). I'm not sure if the radar has any sidelobe reduction techniques (guard antenna for sidelobe cancellation, sidelobe blanking, STC, etc) but if it doesn't then you can expect performance to go out the window down on the deck.